Modified KIT-6 and SBA-15-spherical supported metal catalysts for N2O decomposition

Abstract

Nitric acid and adipic acid plants are the main producers of nitrous oxide (N2O), a greenhouse gas that damages the ozone layer and causes environmental issues. In the present work, an attempt has been made to modify KIT-6 and SBA-15-spherical mesoporous silica to enhance the hydrothermal stability and increase the acidic sites on the surfaces through post salt addition and aluminum (Al) incorporation, respectively, in order to effectively utilize them as supports for different metals (Rh, Ru, Pd, Fe) supported catalysts for N2O decomposition. Each metal loadings of 1wt.% was impregnated onto the modified mesoporous silica support materials. The materials were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), ammonia temperature programmed desorption (NH3-TPD), nitrogen adsorption/desorption, X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis techniques. The potential of these modified mesoporous silica supported Rh, Ru, Pd or Fe (1wt.%) powder catalysts has been examined in a small laboratory scale reactor under specific N2O decomposition conditions. The order of activity of the metals on the modified mesoporous silica supports was: Rh>Ru>Pd>Fe. The modified mesoporous silica supported Rh, Ru and Fe catalysts showed an enhanced activity for N2O decomposition, compared to the non-modified mesoporous silica supported catalysts, due to an increase in the intermediate acidic sites on the supports. However, a different effect was found for the modified mesoporous silica supported Pd catalysts. The hydrothermal stability of the optimized mesoporous silica supported Rh catalysts indicates that these catalysts could be promising candidates for N2O decomposition application.